similar anatomy-altering disorders. The sequence of images is roughly as follows: plain or Control KUB image; immediate X-ray of just the renal area; 5 minute X-ray of just the renal area. 15 minute X-ray of just the renal area. At this point, compression may or may not be applied (this is contraindicated in cases of obstruction). In pyelography, compression involves pressing on the lower abdominal area, which results in distension of the upper urinary tract. If compression is applied: a 10 minutes post-injection X-ray of the renal area is taken, followed by a KUB on release of the compression. If compression is not given: a standard KUB is taken to show the ureters emptying. This may sometimes be done with the patient lying in a prone position. A post-micturition X-ray is taken afterwards. This is usually a coned bladder view. Image assessment The kidneys are assessed and compared for: Regular appearance, smooth outlines, size, position, equal filtration and flow. The ureters are assessed and compared for: Size, a smooth regular and symmetrical appearance. A 'standing column' is suggestive of a partial obstruction. The bladder is assessed for: Regular smooth appearance and complete voiding. Risks Intravenous pyelograms use ionizing radiation, which involves risk to healthy tissues (potentially encouraging cancer or risking birth defects). Therefore, they are often now replaced by ultrasonography and magnetic resonance imaging (MRI). Also, the iodinated contrast medium used in contrast CT and contrast radiography can cause allergic reactions, including severe ones. The contrast dye may also be toxic to the kidneys. Because a cannula is inserted, there is also a risk of a cannula site infection, that may cause fevers or redness of the cannula area. Contraindications Metformin use: Historically, the drug metformin has been required to stop 48 hours pre and post procedure, as it known to cause a reaction with the contrast agent. However, guidelines published by the Royal College of Radiologists suggests this is not as important for patients having <100mls of contrast, who have a normal kidney function. If kidney impairment is found before administration of the contrast, metformin should be stopped 48 hours before and after the procedure. Contrast allergy: If the patient has any previous history of adverse or moderate reactions to contrast medium. Patient with significantly decreased kidney function ;because contrast media can be nephrotoxic and worsen kidney function Anterograde pyelogram Antegrade pyelography is the procedure used to visualize the